A dynamoelectric machine, such as an electric power generator, includes a rotor, a stator surrounding the rotor, and a generator housing surrounding the rotor and stator. The generator produces electrical current as the rotor turns within the stator. The electrical current flows through respective windings mounted on the rotor and stator, and generates heat that may be dissipated away from the rotor and stator for greater generator efficiency and/or reliability.
One technique for cooling the rotor and stator is to circulate a cooling gas within the generator housing. The circulating gas removes heat from the rotor and stator windings. A gas-to-liquid cooler within the generator housing may be used to transfer the heat from the gas to a liquid coolant flowing through the cooler.
Some gas-cooled generators use coolers that extend horizontally in parallel with the axis of the rotor and stator. Although horizontal coolers are still used, later-designed gas-cooled generators typically incorporate one or more coolers positioned vertically within a generator housing. U.S. Pat. No. 2,707,243 to Baudry et al., for example, discloses a pair of vertical coolers positioned between a stator-winding duct and a housing bracket at the end of an electrical generator.
Both types of coolers—horizontal and vertical—are typically rectangularly shaped. U.S. Pat. No. 5,785,114 to Armstrong et al., for example, discloses a cooler that can be positioned either horizontally or vertically, but like other conventional coolers, it is rectangular. Specifically, the cooler comprises a rectangular cooler frame and a plurality of straight, elongate cooling tubes within the rectangular cooler frame.
Horizontal and vertical rectangular coolers pose a number of distinct disadvantages in cooling a dynamoelectric machine, such as an electrical power generator. For example, because a generator typically is positioned on a frame within the generator housing, the frame normally is irregularly shaped and has an enlarged diameter to accommodate the horizontal or vertical rectangular cooler. The result is an increase in the costs of manufacturing and transporting such a dynamoelectric machine.
In cooling such a machine, moreover, the gas is directed away from the generator and toward the cooler, after heat has been transferred from the generator to the circulating gas. Similarly, after the gas has been cooled by the transfer of heat to the coolant within the cooler, the gas is directed to an inlet of a blower to redirect the gas toward the generator to maintain circulation of the cooling gas. With rectangular horizontal or vertical coolers, internal baffles are used to direct heated gas away from the generator and to direct cooled gas to the blower inlet.
Although needed to properly direct the circulating gas, the internal baffles result in greater gas pressure losses. The loss of gas pressure caused by the internal baffles lowers the efficiency of the dynamoelectric machine and typically requires the use of larger blowers to overcome the loss. Not only is the operating efficiency of the dynamoelectric machine reduced as a result, but so, too, the cost of manufacturing is increased owing to the need to install the internal baffles and larger blowers.